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HEAVY DUTY DIESEL ENGINE OIL
Maximized Engine Protection
Extreme Temperature Protection
Proven Clean Performance
Engineered for Emissions
Maximized Engine Protection
Fights thermal breakdown and sludge while maintaining shear stability to protect parts and extend oil life.
Extreme Temperature Protection
Flows fast in freezing temps for reliable cold starts when the job won’t wait.
Proven Clean Performance
Oxidation control helps cut deposits and keeps internal parts running cleaner.
Engineered for Emissions
Meets GHG 17 (Greenhouse Gas 2017) standards to lower carbon output and improve fuel economy.
WHAT OIL IS BEST FOR YOUR TRUCK?
15W-40 FULL SYNTHETIC
The classic heavy-duty diesel oil—tough, proven, reliable. Excellent for hot climates, towing, and high-load conditions. Fits most Cummins, Powerstroke, and Duramax setups with no issues.
5W-40 FULL SYNTHETIC
Best for cold climates since it flows better at startup. Go-to pick for modern turbo diesels like Duramax, Powerstroke, and Cummins. Approved by many OEMs for year-round use where cold starts are common.
10W-30 FULL SYNTHETIC
Provides slightly better fuel economy due to lower viscosity. Recommended by Cummins for some medium-duty trucks. Works best in moderate climates, but may not protect as well in high-heat/heavy towing compared to 15W-40.
15W-40 SEMI-SYNTHETIC
Budget-friendly option that still gets the job done. Offers less extreme temperature performance than full synthetic. Great for fleet trucks or regular oil change intervals.
WHAT OIL IS RIGHT FOR YOU?
15W-40 FULL SYNTHETIC
The classic heavy-duty diesel oil—tough, proven, reliable. Excellent for hot climates, towing, and high-load conditions. Fits most Cummins, Powerstroke, and Duramax setups with no issues.
5W-40 FULL SYNTHETIC
Best for cold climates since it flows better at startup. Go-to pick for modern turbo diesels like Duramax, Powerstroke, and Cummins. Approved by many OEMs for year-round use where cold starts are common.
10W-30 FULL SYNTHETIC
Provides slightly better fuel economy due to lower viscosity. Recommended by Cummins for some medium-duty trucks. Works best in moderate climates, but may not protect as well in high-heat/heavy towing compared to 15W-40.
15W-40 SEMI-SYNTHETIC
Budget-friendly option that still gets the job done. Offers less extreme temperature performance than full synthetic. Great for fleet trucks or regular oil change intervals.
What Your Diesel Deserves
Doc’s Diesel Oils are built to protect hard-working diesel engines, and each formula delivers strong wear protection, low oil consumption, and rock-solid performance in extreme conditions.
What Your Diesel Deserves
Doc’s Diesel Oils are built to protect hard-working diesel engines, and each formula delivers strong wear protection, low oil consumption, and rock-solid performance in extreme conditions.
Customer Reviews
Customer Reviews
Doc’s diesel has proven to have quality parts that i am proud to use in my truck definitely recommend to all my diesel brothers and sisters
I love how easy it was to purchase and the price is great for this high end of oil. My only complaint is the shape of oil container makes it really hard to pour even into a funnel. Apart from that I love the oil
Changed all my filters and oil all at once. •fuel•oil •cab•air•crankcaseIt’s truly a one stop shop. With quality and no price gouging
This oil is a bit more pricey than off the shelf synthetic from your big box store but if you believe that it has been improved on over the off the shelf it seems to be a good deal. I just did a full service on my 2020 Denali Duramax using all Doc’s products and am pleased. Just wish it was all American made products.
I was disappointed on the condition of the outside box that was thrashed. On the inside I found the oil filter rolling around outside of its packaging, and the fuel filter and diesel filter boxes were damaged exposing the filters and gaskets. I do want to try these products out and do believe that this a well thought out brand, but wish the shipment wasn’t such a failure. Thank you.
The oil order was processed and shipped quickly. Ordered it with a filter package and couldn’t be more satisfied. My neighbor a diesel mechanic did the oil change with me, and not that it really matters but the Doc’s oil has a pleasant unique scent to it. Drove the truck for a trip and it honestly seems to run better with this oil.
I've always used Royal Purple and thought it was ok. After switching to Doc's, I noticed an immediate improvement in my trucks performance, fuel mileage, ticking went away and starts much easier.
It’s good oil and filter setup. Great quality filter products too
I have had multiple friends recommend Doc’s to me over the years past year. I switched to it now in my 6.7 cummins and I’m excited to see how it performs. So far my motor has been running 5-8°F cooler.
Smoth ride on my truck perfect oil
FREQUENTLY ASKED QUESTIONS
What’s your shipping policy?
We offer free shipping over $99 on all orders within the contiguous United States. Expedited shipping is available for an additional charge. Alaska, Hawaii, and Canada will have shipping fees.
Where does Doc’s Diesel ship to?
We ship to the U.S. and Canada! For Canada orders, any taxes, duties, or customs fees are the responsibility of the buyer. We handle orders in 1-2 business days, and most of the time in less than 24 hours if ordered on a week day. Depending on location, U.S. orders will arrive between 3-5 business days from your order. Canada orders typically arrive within 7-11 days.
What is your warranty?
View our Official Limited Warranty
Doc’s Diesel Filters meet or exceed Original Equipment Manufacturer’s (OEM) requirements. New vehicle warranties stay in effect when Doc’s Diesel filters are installed correctly and in conjunction to engine manufacturer’s recommendations.
Where is my order?
If you have not received your confirmation email us sales@docsdiesel.com so we can get everything sorted out ASAP. If you received a confirmation but no shipment email, we are still working on your order. Don't hesitate to email sales@docsdiesel.com if you would like more information and we'd be happy to check on your order. Please Include your order # in the email.
For Tracking information, it will be in your shipment email. Check the tracking # first or the latest updates. Doc's Diesel, just like you are at the mercy of shipping companies after a shipment leaves our warehouse. If there's been an issue with shipment we will happily work with you to figure out where the order is and what we can do to help. You can reach out to sales@docsdiesel and include your order # in the email. Thank You!
Why didn’t I get a confirmation email?
Sometimes an email may get sent to your spam folder! So don’t forget to check that. If you need more help to hesitate to reach us at sales@docsdiesel.com.
How do I start a return?
If you are unhappy with your purchase for whatever reason, and it's within 30 days from your purchase, you can return your diesel filters back to us. Item has to be in new condition. Once filters are received, we will refund your money (minus price of return shipping) within 2-4 business days. We will refund to your original form of payment.
To start a return, visit our Returns Center.
View Our Official Limited Warranty Policy
Thank you!